The present invention relates to a projection-type image displaying apparatus, for conducting image display by projecting an image on a image display element(s), enlargedly, upon a tracing or surface, such as a translucent screen, and it relates to a projection display apparatus, in particular, being suitable for a front-projection type image display apparatus, and further a projection optic unit for the same.
For a color image display apparatus for projecting an image on an image display element(s) onto a screen (a tracing picture) through a projection optic unit, being made up with a plural number of lenses, it is requested to obtain an enlarged image having sufficient size or magnitude on a screen, without generating distortion therein. For achieving this, as is disclosed in Japanese Patent Laying-Open No. Hei 5-134213 (1993) or Japanese Patent Laying-Open No. 2000-162544 (2000), for example, there is already known a projection apparatus or an optic system for projecting an image, enlargedly, into the direction an inclined to a screen, while shifting the projection screen into the direction perpendicular to an optical axis of a projection system and also with using an additional optic system, being disposed by inclining by a predetermined angle with respect to that optical axis of the projection system. Herein, the additional optic system (i.e., afocal converter) is an optical system having a function of converting the sizes of projection image, and it is provided for obtaining a rectangular projection image with compensation/reduction upon the distortion of projection image, which is generated accompanying with the projection thereof from the inclined direction onto the screen.
Also, for example, in Japanese Patent Laying-Open No. 2004-157560 (2004), there is already known a reflection-type image forming optical system, for projecting an image on the image display element(s) onto the screen (i.e., the tracing surface), enlargedly, but with using a plural number of reflection mirrors in the place of the lenses mentioned above (i.e., the optic elements within a transmitting system).